May 26, 2015—The next-generation Jeep Wrangler will not have an aluminum body, according to an announcement made last week. The company’s plans for an aluminum Jeep Grand Wagoneer are still in place, however, despite a possible delay in its release.

This is a reversal of what Fiat Chrysler CEO Sergio Marchionne said only one year ago—that there was no better vehicle in the company’s lineup to make from aluminum than the Wrangler.

The decision was a financial one.

"We've run the numbers and we've simulated mileage and the impact. Because of the difference in cost not just of the material but the actual assembly process, I think we can do almost as well without doing it all aluminum," Marchionne said, according to reports.

The off-roader will keep the steel body structure but add aluminum doors, fenders and other parts. The Wrangler is following General Motors’ lead of using aluminum strategically to minimize costs.

The Wrangler, due out in 2017, still needs to lose weight to get a better fuel economy rating that the current 21 mpg. This will be achieved by “hanging” lightweight aluminum doors and other panels onto the steel structure, according to Marchionne.

This development could be great news for Toledo, Ohio, who have been trying to keep Wrangler production there. The steel body means that the Wrangler plant won’t have to be gutted to switch over to aluminum construction. Capacity constraints could still pose a potential problem at the current plant and the final decision about production in Toledo will be made in the next two months.

Sales for the 2014 Wrangler reached a record 175,328 in the U.S. and through April are up another 22 percent. The announcement of the steel body for the Wrangler could be seen as a solid win for the steel industry.

Marchionne’s main concern may be the disruption of production and the expense of switching the Wrangler plant to aluminum production. FCA only has one plant in the world producing the Wrangler, the Toledo Assembly Complex. Shutting down production of the Wrangler would mean an immediate shortage and lost sales of one of the FCA’s most profitable vehicles.

Marchionne implied last week that although the Wrangler will not be aluminum, the coming Jeep Grand Wagoneer will be. Different costs and benefit calculations regarding aluminum will apply to the full-size Grand Wagoneer.

Marchionne said that the Grand Wagoneer’s development might mean a one-year delay in the redesign of the Grand Cherokee, previously due in 2017.

"I think that development [of the Grand Wagoneer] needs to coincide with a complete relook at the Grand Cherokee architecture and effectively jointly develop them. And if there is a delay [in the Grand Cherokee], it's due to the joining of these two programs into something that makes sense," Marchionne said.

The Grand Wagoneer, he said, "needs to happen. There's a piece of the market that I think we have not accessed because of the nature of that [current Grand Cherokee] architecture and what it can offer," the CEO said. "I think we need to go there with the next version."